For this case, the first thing we must do is define a variable.
We have then:
t: number of years
P (t): number of people since 2010
We know that:
1) There were 30,700 people in the city
2) The population is growing at a rate of 850 people per year.
The equation modeling the problem is given by:

Answer:
a formula for the city's population is:
